A suspension substrate mounted with a device such as a magnetic head mounted on a read/write electrical circuit with a suspension is known as a circuit board used for an HDD (a hard disk drive). The suspension substrate ordinarily has a fundamental structure such that a metal supporting substrate (such as SUS), an insulating layer (such as a polyimide resin) and a wiring layer (such as Cu) are laminated in this order, and is ordinarily provided at one tip with a device mounting area to be mounted with the device and provided at the other tip with an external circuit board connecting area to connect with an external circuit board.
A connecting terminal area including a connecting terminal is ordinarily formed in the suspension substrate for electrically connecting the device and the external circuit board. This connecting terminal ordinarily has a flying structure projecting from the metal supporting substrate. The reasons therefor are various, and one of the reasons is conceived to be that unless the connecting terminal has the flying structure, there is a possibility that the insulating layer located under the connecting terminal melts due to heat during solder joining to short-circuit the connecting terminal and the metal supporting substrate. On the other hand, the problem is that the connecting terminal with the flying structure is so weak in mechanical strength as to be easily transformed by reason of not being supported by the metal supporting substrate.
Here, a suspension substrate with a circuit, in which a pattern terminating portion as a connecting terminal for connecting with a terminal of a magnetic head is formed in a circuit pattern and an end face of the pattern terminating portion is aligned with an end face of an insulating layer directly therebelow or projects from an end face of the insulating layer in a tip direction, is disclosed in Japanese Patent Application Publication No. 2006-120288. In addition, the patterning of the insulating layer by etching is described in Japanese Patent Application Publication No. 2006-120288.
Also, it is described in Japanese Patent Application Publication No. 2001-305750 that in an etching method of a polyimide film, a photosensitive resin layer is first disposed on both faces of the polyimide film and subject to exposure and development to thereby form a resist pattern, and next the obtained resist pattern is further subject to ultraviolet-light irradiation to improve the hardness of the resist pattern. In addition, the patterning of an insulating layer by wet etching is described in Japanese Patent Application Publication No. 2001-305750.